Reliable and quick data transmission is essential in the information age. Data transmission over long distances is primarily accomplished by using electro-magnetic carrier waves at different frequencies. Such data transmission may occur through the air by open air transmitters (wireless) or through a transmission medium such as wire. However, such methods are inherently limited by the medium carrying the electro-magnetic waves. In the case of wire, the material properties of metals used to construct the wire limit the speed and bandwidth of data transmission. In the case of open air transmission, transmission signals are subject to interference thus distorting or blocking the signal.
One proposed solution is the use of light based transmitters. Such transmitters use light emissions at different frequencies or bandwidths to encode and carry data. A light transmitter may be used over short distances for wireless communication. Longer distances may be covered using a fiber optic cable. Such light based transmitters theoretically have much greater bandwidths and speed as compared to electromagentic wire transmitters.
One promising application for light based transmission involves the use of optical switches. Previously, optical switches have typically been based on optosensors consisting of a single photodiode, phototransistor, photodarlington, or similar devices, which in each case is a two-state, current-driven device that has an "on" or "off" current state. For applications such as optocouplers and optoisolators, these devices responded to an "on" or "off" pre-coupled signal with a corresponding "on" or "off" post-coupled current-signal. The inherent speed of such devices has been limited by the rate at which they can switch their currents "on" and "off," with a limiting factor often being the passive return-to-ground period. In addition for an "on" current state to be recognized, the current had to be of a significantly greater amplitude than the background noise. However, the higher the signal current that was needed to generate this recognition, the longer it would take for the switch device to generate that current level, and the even longer period before the switch device would return to the ground level. These characteristics of previous optoelectronic switches resulted in relatively slow switching speeds of usually less than 1 MHZ for a standard photodiode, and even slower speeds for more complicated devices such as phototransistors.
Although optoelectronic switches can be designed to respond with faster switch frequencies by using special circuitry, the additional components of such circuitry increase the complexity and cost of such devices. Further, the transmitter and receiving elements of fast optoelectronic switches have had to be in close proximity, usually in a single package, to function efficiently and to minimize extraneous light interference.
Thus, there exists a need for a more efficient use of bandwidth in conjunction with an opsistor-based open air transmission device. There also exists a need for a more efficient use of bandwidth in conjunction with an opsistor-based fiber optics transmission device.